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CM(4) FreeBSD Kernel Interfaces Manual CM(4)
NAMEcm -- SMC Arcnet Ethernet device driver
SYNOPSIS
To compile this driver into the kernel, place the following lines in your
kernel configuration file:
deviceisadevicecm
Alternatively, to load the driver as a module at boot time, place the
following line in loader.conf(5):
if_cm_load="YES"
DESCRIPTION
The cm driver provides support for the Arcnet ISA network adapters.
This driver also has quirks preset in the device.hints(5) file for card
detection.
HARDWARE
The cm driver supports the following card models:
+o SMC90c26
+o SMC90c56
+o SMC90c66 in '56 compatibility mode.
IMPLEMENTATION NOTES
When the NOARP flag is set on the cm interface, it does not employ the
address resolution protocol described in arp(4) to dynamically map
between Internet and Ethernet addresses on the local network. Instead it
uses the least significant 8 bits of the IP address as the hardware
address like described in RFC 1051 and RFC 1201.
With the IFF_LINK0 flag cleared IP/ARP/RARP encoding is done according to
RFC 1201 that is, with Packet Header Definition Standard header and
packet type 212 / 213. The MTU is normally 1500. The IFF_LINK0 flag is
cleared by default.
With the IFF_LINK0 flag set, IP and ARP encoding is done according to the
deprecated RFC 1051 encoding, that is with simple header, packet type 240
/ 241, and the MTU is 507.
When switching between the two modes, use
ifconfig interfacename down up
to switch the MTU.
DIAGNOSTICS
The following driver specific error messages may be reported:
reset:cardreset,linkaddr=0x%02x(cm%d) The card is being reset and
a new link address assigned.
srint:restartedrxonbufcm%d The rx buffer has been emptied and will
be reset.
SEE ALSOnetintro(4), watchdog(4), device.hints(5), ifconfig(8), watchdog(8)HISTORY
The cm device was ported from NetBSD by Max Khon <fjoe@FreeBSD.org> and
first appeared in FreeBSD 4.6. This manual page first appeared in
FreeBSD 5.3.
AUTHORS
This manual page was written by Tom Rhodes <trhodes@FreeBSD.org>. The
IMPLEMENTATIONNOTES section was submitted by
Max Khon <fjoe@FreeBSD.org> and originated from NetBSD.
BUGS
The cm driver code could do with a bit of improvement, it would be nice
if some one could come along and take care of this.
The IMPLEMENTATIONNOTES section is specific to all Arcnet devices (see
sys/net/if_arcsubr.c) and should be moved to a more generic location.
FreeBSD 10.2 July 16, 2005 FreeBSD 10.2